1. Field of the Invention
This invention relates in general to seals, and in particular to a metal seal for sealing a joint between two conduits where large temperature changes occur.
2. Description of the Prior Art
Extreme sealing environments exist where elastomeric seal material properties will not suffice and existing metal seal designs fall short. One main area of need is in sealing environments that experience rapid temperature changes anywhere from 200 degrees F. to 1,000 degrees F. This event occurs when a cooler fluid is introduced into a higher temperature system, such as hydrogen gas at 1300 degrees F. pumped through a seal system operated at 1800 degrees F. This event also occurs in cryogenic applications where liquid hydrogen at minus 423 degrees F. is introduced into a sealed system at ambient temperatures of 70 degrees F.
If the seal is in certain applications, such as a man rated aerospace vehicle, additional concerns exist. Such vehicles must have seals which are redundant. That is, each seal must have a primary seal surface and a secondary seal surface. These seals must operate within the material elastic limits. The seal surfaces must be independently functional such that if leakage occurs past the primary seal, the secondary seal must not be adversely affected. The seals must be compact and lightweight. They must be reliable and be able to bridge over pits and small scratches without reworking.
Furthermore, in certain applications, the seal member must be able to tolerate axial movement, such as movement along the direction of the joint separation. Some joint designs between conduits utilize an arrangement which allows slight axial movement between the two conduits at the joint faces when pressurized. Other joints simply are not strong enough to keep the joint faces completely together when pressure is applied. Other systems experience joint separation after being subjected to temperature variations, corrosion or high temperature.